ES2021244A6 - Tachometric device - Google Patents

Abstract

Device of the type using a magnetic field sensor for detecting the passage of a magnet 7 connected to the rotary piece or shaft 8. It eliminates possible electromagnetic interferences with the sensor and the means for transmitting the signals generated by the sensor, which consists of a rigid body 1 with a through- hole A, B, interrupted by a groove 11 at two points C, D. A movable piece 4 made from flexible material and capable of being attracted by a magnet 7 which is secured to the rigid body 1 and has a hole 6 coincident, at rest, with those of the rigid body 1, is introduced into the groove 11. A transmitting optical fibre 2 and a receiving optical fibre 3, whose free ends are joined to a light source 9 and to a photodetector 10, respectively, are introduced, respectively, via the ends A, B of the through-hole and as far as the groove 11. When the movable piece 4 is attracted by the passage of the magnet 7, it interrupts the transmission of light between the two optical fibres, at the frequency of rotation. In another embodiment, the hole in the rigid body reaches only as far as the groove 11 and the movable piece 4' has no hole. The two optical fibres 2, 3 are inserted via the hole and the movement of the movable piece 4' interrupts reflection of the light between the two optical fibres.